1. Field of the Invention
The present invention relates to a thermoplastic resin composition comprising a liquid crystalline polyester, an aromatic polycarbonate, and specific glass fibers.
2. Description of the Related Art
An aromatic polycarbonate is excellent in impact resistance and so on, but it has a problem that it is an amorphous resin so that it deforms greatly at a temperature around its glass transition temperature (150.degree. C.). In a field where higher stiffness is required, a composition comprising the aromatic polycarbonate and milled glass fibers has insufficient stiffness. While a composition comprising the aromatic polycarbonate and chopped glass fibers having a relatively long length has high stiffness, its recycling property is unsatisfactory.
When much higher stiffness is required, a large amount of the glass fibers should be compounded in the aromatic polycarbonate. Then, a weight of the composition is considerably increased, a molded article of such composition has poor appearance, or a screw or a mold of a molding apparatus tends to be damaged.
Different from a crystalline polyester such as polyethylene terephthalate or polybutylene terephthalate, a liquid crystalline polyester does not suffer from tangling of molecules in a molten state since the molecules are stiff, forms a polydomain having a crystal state, and molecular chain are highly orientated in a flow direction at a low shear. Then, the liquid crystalline polyester is generally called as a thermotropic liquid crystal polymer. Because of such specific behaviors, its melt flowability is excellent and it can easily provide a thin-wall molded article having a thickness of about 0.2 to 0.5 mm, and the molded article advantageously has a high strength and high stiffness, while it has drawbacks that its anisotropy is large and its weld strength is very low. In addition, the liquid crystalline polyester has a high profile processing temperature, its range of application is limited. Further, it is expensive, which is another further problem.
Hitherto, as attempts to solve such drawbacks of each of the aromatic polycarbonate and the liquid crystalline polyester, it has been tried to compensate the physical properties of two polymers by a composition which is obtained by melt kneading the aromatic polycarbonate and the liquid crystalline polyester. Such attempts are disclosed, for example, in Japanese Patent Publication No. 60057/1989, and Japanese Patent KOKAI Publication Nos. 225054/1992 and 102257/1990. However, none of the disclosed compositions has sufficient physical properties.
Japanese Patent KOKAI Publication Nos. 86266/1993 and 86267./1983 disclose compositions comprising a liquid crystalline polyester, a thermoplastic resin and an epoxy compound. However, the compositions have insufficient physical properties. Further, it is not necessarily easy to obtain a composition comprising a resin and an epoxy compound, since the compound which does not contribute to a reaction remains in the composition and may deteriorate the physical properties of the composition.